Thank you very much, my new friends!
Very happy to read your replies, must admit that..
anyway, I have to say that I didn't explain myself as good as I wanted, in my first post..
naturally, at least at hardware level, it clear that same things a person could with Windows he could do with Linux, too! It's a work that it had to be done with the hardware..
But I saw that a lot of people uses special software to take shots of their results.. sometimes are software like CpuZ, sometimes are benchmarking software.. but in same cases I saw GPU's proprietary software (nVidia, Ati ones, just for example): and I really doubt that those kind of software they exist for Linux, too.. I don't understand why, but I fear that that's the truth.. :(